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  • [Bash] Use Conditional Statements in Bash

    Knowing how conditionals work in bash open up a world of scripting possibilities. We’ll learn the basic syntax, including if, else, and elif. Then we'll look at a few of the "primary" operators you can leverage in a conditional statement such as = for string equality, -eq for numeric equality, and -e to check if a file exists. After that, we'll use conditional statements to create a function that asserts that the HTTP status of a given URL is between 200 and 299.

    Basic conditional block:
    
    ```bash
    if [[  ]]; then
    
    fi
    

    Exp:

    if [[ $USER = 'username' ]]; then
      echo "true"
    else
      echo "false"
    fi
    

    not equal: !=
    numeric equality: -eq
    not equals: -ne
    is empty: -z

    if [[ 1 -eq 1 ]];
    
    if [[ -z $USER ]];
    

    Elif

    if [[ -z $USER ]]; then
      echo "user is empty"
    elif [[ 1 -eq 1 ]]; then
      echo "1==1"
    else
      echo "false"
    fi
    

    Ternary

    [[ $USER = 'username' ]] && echo "yes" || echo "no"
    

    Exp:

    check_status() {
      ## Get HTTP status code
      local status=$(curl -ILs $1 | head -n 1 | cut -d ' ' -f 2)
      if [[ $status -lt 200 ]] || [[ $status -gt 299 ]]; then
        echo "$1 failed with a $status"
        return 1
      else 
        echo "$1 succeeded with a $status"
      fi
    }
    
    check_status https://example.com
    check_status https://example.com/404
    
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  • 原文地址:https://www.cnblogs.com/Answer1215/p/14391720.html
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